The present invention relates to a clamping device for fixing a die or a work to be machined by a machine tool on a setting surface of a plate member such as bolster, platen and table.
As to the clamping device for clamping a die of injection molding machine or press machine on a platen or bolster, various clamping devices are presented for practical use as disclosed, for example, in the Japanese Laid-open Utility Model Publication No. 48-44073 and Japanese Patent Publication No. 52-30371.
Particularly, in a horizontal type injection molding machine, a pair of vertical platens is provided, and clamping devices for fixing the die on the setting surface of platen are disposed at both right and left areas of the setting surface.
When exchanging the dies, generally, an overhead traveling crane is used to replace the dies, and in this case, with supporting the die by the wire of the crane, and after releasing the clamping device, the clamping device is set aside on the setting surface, and the used die is lifted upward, and discharged. Then, a next die is lifted by the crane, and is lowered along the setting surface, and the clamping device is moved toward the die, and the die is fixed on the setting surface by the clamping device.
When the die size is changed by exchange of dies, moreover, the mounting position of the clamping device must be changed.
On the setting surface of a horizontal type injection molding machine, generally, any T-groove is not formed, but plural tap holes are formed in a specific layout pattern. Accordingly, as to the clamping device, it is preferable to apply a clamping device capable of being fixed on the setting surface through the tap holes and bolts, and being changed over the position in the state of being mounted on the setting surface.
For example, the clamping device disclosed in the Japanese Utility Model Publication No. 58-54990 is put in practical use. In this clamping device, a slit is formed in the clamp arm, and a fulcrum bolt penetrating through a bolt hole of a holding plate to be engaged with the upper end of the clamp arm and the slit in the clamp arm is screwed into the tap hole of the setting surface, and the rear end portion of the clamp arm is supported on the setting surface through a spacer and a bolt member. By tightening the fulcrum bolt, the die is fixed on the setting surface with the front end portion of the clamp arm.
In such injection molding machine or press machine, when exchanging the dies, the clamping device is once set aside and the old die is removed, and a new die is put in, then the clamping device is set at the clamping position for fixing the new die.
In the clamping device disclosed in the Japanese Patent Publication No. 52-30371, since the clamp main body is fixed on the setting surface with bolts, it takes a lot of time and labor for changing over the position of the clamping device. The clamping device disclosed in the Japanese Laid-open Utility Model Publication No. 48-44073 can not be mounted on the setting surface on which T-groove is not formed, such as the setting surface of the injection molding machine.
On the other hand, the clamping device disclosed in the Japanese Utility Model Publication No. 58-54990 can be mounted by utilizing the existing tap holes of the setting surface, and also can be changed over the position of the clamp arm by loosening the fulcrum bolt. In the releasing state, however, since the clamp arm and fulcrum bolt are not coupled at all, they tend to separate from each other, and their handling or storing may be troublesome.
This clamping device is light in weight, and is hence desirable for fixing the die on the vertical setting surface of the lateral injection molding machine, but since it cannot generate powerful clamping force, multiple clamping devices are needed, and it is difficult to improve the working efficiency of clamping and releasing, and parts may be dropped in releasing state, among other problems.
It is hence a primary object of the present invention to mount a clamping device on the setting surface by utilizing the existing tap holes of the setting surface, to simplify the position changeover operation of the clamping device, to improve the working efficiency of clamping and releasing, and to reinforce the clamping force.